1. Field of the Invention
The present invention relates to a light-receiving member which has a sensitivity to electromagnetic waves such as light (hereafter light is defined in the broad sense of the word and includes ultraviolet rays, visible rays, infrared rays, X rays, .lambda. rays, etc.), more specifically, a light-receiving member which is important in the field of image formation by an electrophotographic copying machine or the like and a method of producing the light-receiving member.
2. Related Background Art
In the field of image formation, a photoconductive material which forms a light receiving layer in a light-receiving member is required to provide a high sensitivity, a high S/N ratio [optical current (Ip)/dark current (Id)], an absorption spectrum adapted to spectral characteristics of irradiated electromagnetic waves, quick response to light, and required dark resistance and is harmless to human bodies during use. Particularly, for a light-receiving member for electrophotography to be incorporated in electrophotographic copiers to be employed at offices as office equipment, pollution-free harmlessness is an important point.
Amorphous silicon (hereafter referred to as "a-Si") is a photoconductive material which has been lately noted afresh from the viewpoint as described above and an application of amorphous silicon as a light-receiving member for electrophotography has been disclosed, for example, in U.S. Pat. No. 4,265,991.
FIG. 1 schematically shows an example of a layer structure of a light receiving layer 104 for electrophotography wherein 101 is a conductive substrate, 102 is a light receiving layer made of a-Si and 103 is a surface protective layer. This light-receiving member for electrophotography is generally made by heating a conductive substrate 101 to 50.degree. to 400.degree. C. and depositing a light receiving layer 102 made of a-Si on the conductive substrate by a film forming method such as a vacuum depositing method, a sputtering method, an ion plating method, a thermal CVD method, an optical CVD method and a plasma CVD method. Particularly, the plasma CVD method, that is, a method for decomposing starting gases through glow discharging with a direct current, a high frequency of microwaves and forming an a-Si deposited film on the conductive substrate, has been implemented as an appropriate method.
On the other hand, amorphous silicon carbide (hereafter referred to as "a-SiC") is known for its high thermal resistance and surface hardness, higher dark resistance than a-Si and possible variations of an optical band gap in a range of 1.6 to 2.8 eV in accordance with the content of carbon. A light-receiving member for electrophotography whose photoconductive layer is formed with such a-SiC has been proposed in U.S. Pat. No. 4,471,042. This patent has disclosed that excellent electrophotographic characteristics including high dark resistance and high optical sensitivity could be obtained by using an a-Si, which contains 0.1 to 30 atomic % of carbon as a chemically modified substance, as a photoconductive layer for the light-receiving member for electrophotography.
Though a conventional photoconductive light-receiving member for electrophotography made of a-Si material has been improved in such characteristics as dark resistance, sensitivity, electrical, optical and photoconductive characteristics, environmental conservation, aging stability and durability, there is in fact still room for further improvement of general characteristics along with those demands for higher sensitivity and durability.
For designing a photoconductive member with the a-Si material, another improvement is required so that the desired characteristics as described above may be obtained.
Designing of a layer structure containing carbon atoms for a photoconductive member enables one to obtain a photoconductive member which excels in the charge maintaining performance in charge treatment, reduces an influence of residual potential on formation of images, provides stable electrical characteristics, high sensitivity and high S/N ratio even in a highly moist atmosphere, and also obtain high quality visible images with clear half tone and high resolution which excel in light-proof fatigue and repeatability and has a high hardness.
However, the content of boron atoms varies along with variations of the content of the carbon atom content in reference to the silicon atom content and therefore actual designing of the layer structure has been very difficult. Hence the light-receiving member for electrophotography has been produced and the determination on a layer structure and designing of the layer structure have been experimentally conducted by evaluating its electrophotographic characteristics.
However, it has been demanded to make it possible to design the layer structure by a simple method for improvement of general characteristics and reduction of overall costs and the period of development.